1. The Field of the Invention
The present invention generally relates to synchronizing data within a distributed computer system. More particularly, the present invention provides for an improved system for detecting when data has changed on a device and for detecting low fidelity sync data.
2. Background and Related Art
Laptop, handheld, and other portable computers or computing devices have increased in popularity as the devices become smaller in size and less expensive. Additionally, improved operating speed and processing power of portable computers has increased their popularity. Many portable computers are capable of storing multiple application programs, such as address books, games, calculators, and the like. The application programs can be permanently installed in the portable computer during manufacture (e.g., on Read-Only Memory (ROM)). Alternatively, one or more application programs may be installed by the user after purchasing the portable computer.
With the increased popularity and computing power of such devices, people are beginning to store data and applications using more than just a single computing device. Many people, for example, often use laptop computers in addition to their regular desktop computer. Other devices such as cellular telephones, Personal Digital Assistance (PDAs), Internet services, and the like are also used for storing data and applications.
Each of these computing devices may be part of a distributed computing system wherein related information can be correlated and stored on multiple such devices. For example, a user may have a digital address book stored on their desktop work computer, on their PDA, on their mobile phone, on an Internet service, etc. Accordingly, while at work, it may be convenient for the user to access contact information, which may include phone numbers and other general contact information. While away from work, however, the user may be able to use the address book in a mobile form such as a personal digital assistance (PDA) or other mobile information storage system. Ideally, the contact information of the PDA should match the contact information at the desktop work computer.
When the same or related information is stored in two places, it is possible for the data to change in one location and not in the other. This problem may be overcome through synchronization, which is an automated process that attempts to ensure that each device within the distributed system has the most current information or data. Synchronization, however, has its own set of problems. For example, when synchronization is initialized between the two devices, current systems detect changed property values by comparing corresponding property values from each device. Such comparison, however, gives no indication as to which device made the change. As such, when a property change has occurred on either device, a conflict occurs and a conflict resolution process must be performed.
Other systems mark a changed property with a tag indicating that a change has occurred, e.g., “change,” “delete,” “add,” or other tag, as appropriate. In such systems, however, each device within the distributed computing system must have the ability to tag a property when it has changed. Many legacy devices, however, don't have such capabilities, and therefore conflicts will still result and need to be reconciled.
Typically, conflicts can be resolved through comparing metadata associated with the property values that give, e.g., time-date information. The latest time-date information is considered the most up-to-date information and the properties can be updated accordingly. Alternatively, a user interface (UI) can be presented to the user in order to resolve the conflict.
In any event, having to resolve the conflict consumes processing resources and is particularly problematic when the data to be synchronized does not include time-date information, which is referred to as low fidelity data. For example, many smaller computing devices have limited physical resources and are incapable of maintaining time-date information for properties of a data structure item. As such, when a computer syncs data in from such low fidelity device, it doesn't know when the user originally set that property. This prevents the computer from syncing in a property from another computing device and confidently using “last-writer-wins” resolution logic to pick the most up-to-date property. Further, even if no conflict existed, there is typically no way to sync the property change to the receiving device without a conflict resolution process. In addition, even if the low fidelity data could be synced, there would be no way to indicate to other devices that the data was received from a low fidelity source.